简化外部热耦合双精馏塔的控制与优化

Control and optimization of simplified externally heat-integrated double distillation columns

针对具有3个换热器结构的外部热耦合双精馏塔(S-EHIDDiC),提出了一种新型的控制与优化策略。顶部与底部换热器的热负荷能够改变高压精馏塔的回流量和低压精馏塔的上升汽量,因而可以用来控制高压精馏塔塔顶和低压精馏塔塔底的产品质量。这种控制方法与常规精馏塔的LV控制结构相似。S-EHIDDiC还有多余的决策变量(如进料分流比,高压精馏塔塔压和中间换热器的热负荷),可以对稳态操作进行优化。闭环仿真证明了这种控制结构的可行性,稳态优化也提高了系统的热力学效率。

A new control structure of the simplified externally heat-integrated double distillation columns（S-EHIDDiC）is proposed,where three heat exchangers are used to approximate external heat integration between the rectifying/stripping sections of the high-pressure（HP）/ low-pressure（LP）distillation columns.The heat duties of the top/bottom heat exchangers are used to control the top/bottom product qualities of the HP/LP distillation columns.Manipulating the heat duties of the heat exchangers serves to change the reflux/reboiled flows of the HP/LP distillation columns,and it is,in principle,similar to the LV control of conventional distillation columns.Some additional decision variables exist in the S-EHIDDiC（i.e.,the feed splitting ratio,the pressure of the HP distillation column,and the heat duty of the intermediate heat exchanger）and can be utilized to minimize utility consumption.The proposed control scheme is evaluated and its feasibility is demonstrated.Improvement in thermodynamic efficiency can also be achieved with the adjustment of those additional decision variables.